In the development of food products for humans, medicines and other products that are orally ingested by humans and animals, the flavor of the products is often the focus of considerable testing and analysis. A product's flavor is in large part determined by the diverse mixture of volatile and relatively non-volatile chemical components released into the mouth and nose of a subject during chewing and oral processing of the product. See Heath and Reineccius "Flavor and Its Study", Flavor Chemistry and Technology, (Connecticut:AVI 1986).
By analyzing the volatile and relatively non-volatile components released from food and other products during oral processing, it is possible to identify the components that contribute to desirable flavors, as well as those components that produce undesirable flavors. Moreover, if such an analysis is conducted over a period of time, then it is possible to determine the release rate of both those desirable and undesirable flavor components throughout oral processing, as well as during an "after taste" period following ingestion of the product. Volatile and relatively non-volatile flavor components are released into the vapor phase so that they circulate throughout the subject's mouth and nose. The release of these components is controlled by highly variable and complex interactions between individual flavor components and the food matrix, as well as a number of oral factors such as chewing, saliva, etc. See Overbosch, Afterof and Haring, "Flavor Release in the Mouth", Food Review International, 7(2), 137-184 (Marcel Dekker 1991). Because these interactions are difficult to predict, it is often necessary to identify and measure the volatile and relatively non-volatile components actually released by a food product, or other products, into a subject's oral cavity or mouth headspace. This is particularly true during the development of reduced fat or reduced calorie substitutes for full-fat or full-calorie food products.
In such products, the amounts of the flavor components released by the products and their release rates during oral processing have a large effect on the products' perceived overall flavor. The relative amounts of each released volatile and relatively non-volatile flavor component, which vary over time, actually dictate the products' perceived flavor. The relative release rate of each volatile and relatively non-volatile component also affects the "staying power" of that perceived flavor. As mentioned above, the release rate of flavor components may be affected by the food product matrix and the manner in which the product is orally processed, i.e. by chewing and circulation of liquid and semi-liquid components in the subject's mouth. Hence, it is often desirable to study both the relative amounts and the release rate of particular flavor components during oral processing over a predetermined time period.
Data on the identity, relative amounts and release rates of volatile and relatively non-volatile components may be used to increase or decrease the amount of certain volatile and relatively non-volatile components in the product, as well as to adjust elements of the food matrix itself. This may include changes in the product recipe or formulation, or changes in the preparation steps for the product. The data may also be used to tailor the flavor of a product for a specific purpose or for a specific audience. The data further may be used to determine changes in released flavor components caused by alterations in the preparation or processing of a product for cost efficiency or other reasons.
Common methods used to analyze volatile and relatively non-volatile flavor components in foods were designed primarily to quantify the total amounts of flavor components in the products before oral processing. Such methods, however, typically did not measure the amount of volatile or relatively non-volatile flavor components actually released from food products into the mouth headspace and nose of a subject during oral processing, nor were they adapted to study the release rates of those components.
Similarly, common approaches for measuring the content of breath samples were not well suited for the study of flavor components in foods and other orally ingested products. See e.g., Soeting and Heidema, Chemical Senses, 13, 607 (1988). One system included a mouthpiece and a tube for carrying the exhaled breath of the subject into a mixing chamber. A sample outlet and exit tube connected the mixing chamber to a measuring device, such as a mass spectrometer. In addition, heat was applied to the system to prevent condensation of moisture from the breath sample on the system components. The mixing chamber insured that the exhaled breath sample mixed with previous samples, and that a small quantity of the combined breath sample was drawn from the chamber into the measuring device. Such approaches were for use in clinical toxicology, occupational medicine and exercise physiology studies.
Another approach used a pumping system to draw an air sample from the nose of a subject, through a glass nose-piece and past a membrane separator fitted to a quadrapole mass spectrometer. In that approach, the subjects also manipulated the sample in their mouth. Other systems have used a solid state sensor adapted to measure one component from a breath sample, such as pentane. In that type of system, a carrier gas and a breath sample were injected into a separating column and were then circulated toward a solid state sensor.
Those prior systems generally required continuous respiration by the subject into tubes or interfaces. Certain of these approaches, in addition, did not provide for sampling components from the mouth headspace. Some systems, in fact, were designed to exclude "dead air" from the mouth, throat, nasal passages and bronchial tubes of a subject.
More importantly, the prior approaches were intended to generally study a single gas such as oxygen or carbon dioxide or only a single component in a breath sample. In approaches using a mass spectrometer, it was possible to measure more than one ion and thus more than one compound at a time, but the sensitivity of the resulting measurements was reduced. Most prior approaches also were not designed to measure a range of volatile and relatively non-volatile components released into the mouth headspace and nose of a subject during oral processing of a food or similar product. Moreover, in some prior applications, the systems did not collect sufficient amounts of the volatile components to accurately measure flavor components released in very small quantities.
The present invention provides a method and apparatus that will measure and analyze both volatile and relatively non-volatile components released from food or other products during oral processing. The method of the invention efficiently collects breath samples from a subject at predetermined time intervals so that the nature and amounts of flavor components actually released by a product during oral processing can be determined. Moreover, the method of the invention does not require continuous sampling, but permits the storage of samples for a limited period so that they can be studied later at the user's convenience.
The method of the invention, in addition, can be used to measure components that are present in small concentrations, yet are important to the flavor of a product. The method is also well suited for measuring a variety of different classes of flavor compounds that may be released by a given product. The invention, further, is cost effective and requires only a limited amount of custom designed equipment.